Water soluble polymers as alcohol replacement in lithographic fountain solutions

Abstract

Isopropyl alcohol is partially or completely replaced in an acid fountain solution for lithographic printing by a hydroxypropylcellulose or similar polymer with a molecular weight below 100,000 where a 30% by weight solution of the polymer has a viscosity below 4000 cps at 25°. Printing quality is improved and scumming is controlled when a hydrogen peroxide degraded hydroxypropylcellulose or hydrophobically modified hydroxyethylcellulose replaces alcohol in a fountain solution.

What is claimed is: 
     
       1. An improved lithographic printing fountain solution comprising: (a) an aqueous solution of a oxidatively degraded hydroxypropylcellulose or oxidatively degraded hydrophobically modified hydroxyethyl cellulose with a molecular weight between 5,000 and 100,000 wherein a 30% by weight solution has a viscosity below 4000 cps at 25° C.;   (b) a desensitizing agent;   (c) an acid and a buffer; and   (d) a wetting agent or surfactant; where the aqueous solution is used in an amount of about 1% by weight of the weight of the fountain solution.     
     
     
       2. The fountain solution of claim 1 having a pH of 5.0 or less. 
     
     
       3. The fountain solution of claim 2 containing hydroxypropylcellulose. 
     
     
       4. The fountain solution of claim 3 further comprising a preservative. 
     
     
       5. The fountain solution of claim 4 where the preservative is methyl parasept. 
     
     
       6. A method for using a fountain solution comprises the steps: (a) replacing 10% by weight alcohol in a fountain solution with a hydroxypropylcellulose or hydrophobically modified hydroxyethyl-cellulose solution degraded with hydrogen peroxide to a molecular weight below 100,000 to prepare an acid fountain solution; and   (b) applying the acid fountain solution to a printing plate to control scumming and to improve printing quality.   
     
     
       7. The method of claim 6 where the polymer is selected from hydroxypropylcellulose, hydrophobically modified hydroxyethylcellulose. 
     
     
       8. The method of claim 7 where the polymer is hydroxypropylcellulose. 
     
     
       9. The method of claim 8 where the fountain solution pH is 5.0 or below.